A self-cleaning cycle is often employed in a domestic stove or oven to clean the interior surfaces of the oven. In a customary manner, the oven interior is raised to a sufficiently high temperature to cause thermal decomposition of grease, grime, and other material in the oven. The temperatures achieved in the oven during the self-cleaning cycle may reach or surpass those which cause pyrolysis of the grease and grime. It is desirable for safety reasons to cover and protect or shield the one or more transparent panes in the window of an oven door from thermal radiation generated in an oven operating at high temperatures. Various types of systems are used to raise and lower a shield to cover the one or more window panes mounted on the outer panel of the oven door, to guide the movement of the shield within the oven door, and to lock the oven door shut during the operation of the oven at higher temperatures. Some systems involve the manual grasping of lugs exterior of the inner panel of the oven door to provide for manual raising and lowering of the shield. Other systems involve raising the shield to the window covering position as the oven door is being locked shut. This usually entails a complex linkage mechanism which amplifies the relative short distance of travel or rotational movement of the locking mechanism to cause the shield to move a much greater distance to cover the window. The shield may be mounted on or connected to a track system which supports the shield on both sides. This type of shield mounting can result in jamming due to thermal expansion and contraction of the metal in the shield and track system. In systems which involve simultaneous raising of the shield and locking the oven door shut, should there be a malfunction in the mechanism for raising the shield, the oven would be activated for self-cleaning without shielding of the door window panes.
It is therefore an object of the invention to provide an apparatus which automatically raises and lowers the shield in an oven door to and from a window covering position, as the oven door is respectively raised from and lowered to an oven door open position.
It is another object of the invention to provide an improved track system for suspending or mounting the shield within the oven door in a cantilever manner so that the unsupported end of the shield is free to move in accommodating thermal expansion within the shield.
It is yet another object of the invention to provide guidance means on the free end of the shield as it is mounted in a cantilever manner, to insure that the shield does not interfere with parts internally of the oven door as the shield is raised and lowered.
It is a further object of the invention to provide an improved locking means to lock the oven door shut when it is operating at high temperatures, the locking means being activated only when the shield is in the window covering position.